The present invention relates to the field of waste containers and, more specifically, to a waste container with a door latch assembly for locking and sealing a door against the container.
The problem of waste handling, waste transport and disposal has become increasingly urgent in our highly industrialized society. Liquid and solid wastes of all kinds, both toxic and nontoxic, are generated by industrial plants, hospitals, laboratories, mining operations and consumers. These materials are accumulated in extremely high volume and must be handled, transported and disposed of without undue risk to the public health and safety, or to handling personnel.
Hazardous waste is frequently transported to disposal sites in large waste containers. These waste containers are typically subject to rough handling and must therefore be of a sturdy construction. During normal use some damage or misalignment of closure members and their associated seals inevitably occurs. This can result in leakage of the container during stationary use or transport, with consequent risks, or costly down-time while the container is being repaired.
Waste disposal is typically accomplished by dumping the waste container contents at an appropriate disposal site. Dumping occurs by opening a rear door at one end of the waste container, raising the other end of the container and permitting the waste to slide through the open rear door. Releasing the seal on the door, even while the container is level, can result in a seepage of contents, particularly when an inner bag liner is not used.
Waste containers within the field of the present invention may be designed for rail transport (intermodals) or for road transport by vehicles equipped with roll-off hoists (roll-off containers). With either container design, the door latching and sealing mechanisms must be constructed to withstand the considerable internal forces generated against the door by the waste within the container. Due to the presence of potentially hazardous waste, the door must also be latched in a manner that will not permit it to be accidentally opened. For a given application (for example, the transportation of liquid sludge), the door latch must typically provide a liquid-tight seal of the door against the container. Also, since government regulations currently limit the fume emissions from containers carrying certain hazardous waste laden with benzene, toluene and other toxic substances, an air-tight (hermetic) door seal may be required in certain applications.
A typical waste container might be about 20 feet long, about 6-8 feet wide, and about 4-7 feet high, although larger or smaller containers are used, and may contain as much as 2000-6000 gallons or more of liquid waste, such as sludge. Since there are 8.4 pounds in each gallon of water, it will be appreciated that as much or more than 20,000-50,000 pounds of liquid waste can be contained in a single waste container. Also, the liquid waste is a moving, dynamic load. As the container stops and starts (as occurs with either rail or vehicle transport), the liquid waste will tend to move back and forth between the front and the rear of the container. During this movement, the maximum flow velocity of the liquid waste will occur in the middle section of the container, as the boundary layers at the floor, roof and sidewalls of the container are areas of zero flow velocity. Therefore, the middle section of the rear door will be the area in which the greatest outward force generated by the hydrostatic pressure of the moving liquid waste against the door will be concentrated. This can cause the rear door, and particularly the center portion of the rear door, to bow outwardly during container transport, unless it is prevented from doing so.
Due to the large door size associated with waste containers which are the subject of this invention, it has been found that multiple door latch mechanisms may be required at each opposing door end adjacent the container sidewalls, and at middle or intermediate sections along the door. Also, due to applicable rail and vehicular transport regulations which narrowly constrain both container size and the size of devices which may outwardly extend from the containers, door latch mechanisms typically must be provided which can be stored closely adjacent to the container sides during transport.
The door latch mechanism must also be highly reliable since the environmental and legal consequences of allowing hazardous waste to leak through an unsealed door can be severe. For this reason, chains or a simple over-center latching mechanism are not desirable, since such latch mechanisms can be accidentally opened.
Known door latch and sealing mechanisms, such as those disclosed in U.S. Pat. No. 4,643,331 to May and U.S. Pat. No. 4,545,523 to Galbreath, are relatively complicated and can be difficult for the operator to use.
Therefore, there is a need for a relatively simple door latch and sealing mechanism which can provide a reliable liquid-tight or hermetic door seal in a variety of transport or weather conditions, which is easily used and maintained, and which can be adjusted to control the tightness of the door seal.